Throughout this application various publications are referenced within parentheses. The disclosures of these publications in their entireties are hereby incorporated by reference in this application in order to more fully describe the state of the art to which, this invention pertains.
1. The Field of the Invention
This invention relates to the medical arts. It relates to a method of diagnosing and treating small intestinal bacterial overgrowth (SIBO), and conditions caused by SIBO. 2. Discussion of the Related Art
Small intestinal bacterial overgrowth (SIBO), also known as small bowel bacterial overgrowth (SBBO), is an abnormal condition in which aerobic and anaerobic enteric bacteria from the colon proliferate in the small intestine, which is normally relatively free of bacterial contamination. SIBO is defined as greater than 106 CFU/mL small intestinal effluent (R. M. Donaldson, Jr., Normal bacterial populations of the intestine and their relation to intestinal function, N. Engl. J. Med. 270:938–45 [1964]). Typically, the symptoms include abdominal pain, bloating, gas and alteration in bowel habits, such as constipation and diarrhea.
Irritable bowel syndrome, Crohn's disease, chronic fatigue syndrome, chronic pelvic pain syndrome, fibromyalgia, depression, attention deficit/hyperactivity disorder, autism, and autoimmune diseases, e.g., multiple sclerosis and systemic lupus erythematosus, are all clinical conditions of unclear etiology. No association has been made heretofore between any of the afore-going diagnostic categories and SIBO.
Irritable bowel syndrome (IBS) is the most common of all gastrointestinal disorders, affecting 11–14% of adults and accounting for more than 50% of all patients with digestive complaints. (G. Triadafilopoulos et al., Bowel dysfunction in fibromyalgia, Digestive Dis. Sci. 36(1):59–64 [1991]; W. G. Thompson, Irritable Bowel syndrome: pathogenesis and management, Lancet 341:1569–72 [1993]). It is thought that only a minority of people with IBS actually seek medical treatment. Patients with IBS present with disparate symptoms, for example, abdominal pain predominantly related to defecation, alternating diarrhea and constipation, abdominal distention, gas, and excessive mucus in the stool.
A number of possible causes for IBS have been proposed, but none has been fully accepted. (W. G. Thompson [1993]). These hypotheses included a fiber-poor Western diet, intestinal motility malfunction, abnormal pain perception, abnormal psychology or behavior, or psychophysiological response to stress.
A high fiber diet increases stool bulk and shortens gut transit time. However the presence of IBS in non-Western countries, such as China and India, and the failure of dietary fiber supplements to treat IBS in double-blind clinical trials are inconsistent with the “fiber hypothesis” for the causation of IBS. (W. Bi-zhen and P. Qi-Ying, Functional bowel disorders in apparently healthy Chinese people, Chin. J. Epidemiol. 9:345–49 [1988]; K. W. Heaton, Role of dietary fiber in irritable bowel syndrome. In: R. W. Read [ed.], Irritable bowel syndrome, Grune and Stratton, London, pp. 203–22 [1985]; W. G. Thompson et al., Functional bowel disorders and functional abdominal pain, Gastroenterol. Int. 5:75–92 [1992]).
Those experiencing chronic IBS pain are often depressed and anxious. Treatment with tricyclic antidepressants has been used to raise the pain threshold of some IBS patients. (W. G. Thompson [1993]). Abreu et al. and Rabinovich et al. taught the use of corticotropin-releasing factor antagonists to relieve stress-related symptoms, including depression and anxiety, in IBS, anorexia nervosa, and other disorders. (M. E. Abreu, Corticotropin-releasing factor antagonism compounds, U.S. Pat. No. 5,063,245; A. K. Rabinovich et al., Benzoperimidine-carboxylic acids and derivatives thereof, U.S. Pat. No. 5,861,398). Becker et al taught the use of serotonin antagonists to treat depression and anxiety associated with IBS and other conditions. D. P Becker et al., Meso-azacyclic aromatic acid amides and esters as serotonergic agents, U.S. Pat. No. 5,612,366).
Those with IBS symptoms have not been shown to have a different psychological or psychosocial make-up from the normal population. (W. E. Whitehead et al., Symptoms of psychologic distress associated with irritable bowel syndrome: comparison of community and medical clinic samples, Gastroenterol. 95:709–14 [1988]). But many IBS patients appear to perceive normal intestinal activity as painful. For example, IBS patients experience pain at lower volumes of rectal distention than normal or have a lower than normal threshold for perceiving migrating motor complex phase III activity. (W. E. Whitehead et al., Tolerance for rectosigmoid distension in irritable bowel syndrome, Gastroenterol. 98:1187–92 [1990]; J. E. Kellow et al., Enhanced perception of physiological intestinal motility in the irritable bowel syndrome, Gastroenterol. 101(6): 1621–27 [1991]).
Bowel motility in IBS patients differs from normal controls in response to various stimuli such as drugs, hormones, food, and emotional stress. (D. G. Wangel and D. J. Deller, Intestinal motility in man, III: mechanisms of constipation and diarrhea with particular reference to the irritable bowel, Gastroenterol. 48:69–84 [1965]; R. F. Harvey and A. E. Read, Effect of cholecystokinin on colon motility on and symptoms in patients with irritable bowel syndrome, Lancet i: 1–3 [1973]; R. M. Valori et al., Effects of different types of stress and “prokinetic drugs” on the control of the fasting motor complex in humans, Gastroenterol. 90:1890–900 [1986]).
Evans et al. and Gorard and Farthing recognized that irritable bowel syndrome is frequently associated with disordered gastro-intestinal motility. (P. R. Evans et al., Gastroparesis and small bowel dysmotility in irritable bowel syndrome, Dig. Dis. Sci. 42(10):2087–93 [1997]; D A. Gorard and M. J. Farthing, Intestinal motor function in irritable bowel syndrome, Dig. Dis. 12(2):72–84 [1994]). Treatment directed to bowel dysmotility in IBS includes the use of serotonin antagonists (D. P Becker et al., Meso-azacyclic aromatic acid amides and esters as serotonergic agents, U.S. Pat. No. 5,612,366; M. Ohta et al., Method of treatment of intestinal diseases, U.S. Pat. No. 5,547,961) and cholecystokinin antagonists (Y. Sato et al., Benzodiazepine derivatives, U.S. Pat. No. 4,970,207; H. Kitajima et al., Thienylazole compound and thienotriazolodiazepine compound, U.S. Pat. No. 5,760,032). But colonic motility index, altered myoelectrical activity in the colon, and small intestinal dysmotility have not proven to be reliable diagnotic tools, because they are not IBS-specific. (W. G. Thompson [1993]).
Because there has been no known underlying cause for IBS, treatment of IBS has been primarily directed to symptoms of pain, constipation or diarrhea symptoms.
For example, administration of the polypeptide hormone relaxin, used to relax the involuntary muscles of the intestines, is a treatment taught to relieve the pain associated with IBS. (S. K. Yue, Method of treating myofascial pain syndrome with relaxin, U.S. Pat. No. 5,863,552).
Borody et al. taught the use of a picosulfate-containing laxative preparation to treat constipation in IBS, small intestinal bacterial overgrowth, and acute or chronic bacterial bowel infections. (T. J. Borody et al., Picosulfate-containing preparation for colonic evacuation, U.S. Pat. No. 5,858,403). Barody also taught the use of an anti-inflammatory agent to treat IBS. (T. J. Barody, Treatment of non-inflammatory and non-infectious bowel disorders, U.S. Pat. No. 5,519,014). In addition, constipation in IBS has been treated with amidinourea compounds. (J. Yelnosky et al., Amidinoureas for treating irritable bowel syndrome, U.S. Pat. Nos. 4,701,457 and 4,611,011).
Kuhla et al. taught the use of triazinone compounds to relieve IBS symptoms of constipation, diarrhea, and abdominal pain. (D. E. Kuhla et al., Triazinones for treating irritable bowel syndrome, U.S. Pat. No. 4,562,188). And Kitazawa et al. taught the use of napthy- and phenyl-sulfonylalkanoic acid compounds to treat IBS symptoms. (M. Kitazawa et al., Naphthysulfonylalkanoic acid compounds and pharmaceutical compositions thereof, U.S. Pat. No. 5,177,069; M. Kitazawa et al., Phenylsulfonylalkanoic acid compounds and pharmaceutical compositions thereof, U.S. Pat. No. 5,145,869). Day taught an IBS treatment involving the administration of an anion-binding polymer and a hydrophilic polymer. (C. E. Day, Method for treatment of irritable bowel syndrome, U.S. Pat. No. 5,380,522). And Borody et al. taught the use of salicylic acid derivatives to treat IBS. (T. J. Borody et al., Treatment of non-inflammatory and non-infectious bowel disorders, U.S. Pat. No. 5,519,014).
A probiotic approach to the treatment of IBS has also been tried. For example, Allen et al. described the use of a strain of Enterococcus faecium to alleviate symptoms. (W. D. Allen et al., Probiotic containing Enterococcus faecium strain NCIMB 40371, U.S. Pat. No. 5,728,380 and Probiotic, U.S. Pat. No. 5,589,168). Borody taught a method of treating irritable bowel syndrome by at least partial removal of the existing intestinal microflora by lavage and replacement with a new bacterial community introduced by fecal inoculum from a disease-screened human donor or by a composition comprising Bacteroides and Escherichia coli species. (T. J. Borody, Treatment of gastrointestinal disorders with a fecal composition or a composition of bacteroides and E. coli, U.S. Pat. No. 5,443,826).
Fibromyalgia (FM) is a syndrome of intense generalized pain and widespread local tenderness, usually associated with morning stiffness, fatigue, and sleep disturbances. (F. Wolfe, Fibromyalgia: the clinical syndrome, Rheum. Dis. Clin. N. Amer. 15(1):1–17 [1989]). Fibromyalgia is often associated with IBS (34–50% of FM cases) or other gastrointestinal symptoms, Raynaud's phenomenon, headache, subjective swelling, paresthesias, psychological abnormality or functional disability, sometimes with overlapping symptoms of coexisting arthritis, lower back and cervical disorders, and tendonitis. Fibromyalgia affects 1–5% of the population and is more prevalent among women than men. (G. Triadafilopoulos et al. [1991])
As in IBS a diagnosis of FM correlates with a decreased pain threshold among FM patients compared to non-patients. (F. Wolfe et al., Aspects of Fibromyalgia in the General Population: Sex, Pain Threshold, and Fibromyalgia Symptoms, J. Rheumatol. 22:151–56 [1995]). But other conventional laboratory evaluations of FM patients are uniformly normal. (G. Triadafilopoulos et al. [1991]). The symptoms of FM patients are typically treated with anti-inflammatory agents and low dose tricyclic antidepressants. Administration of relaxin for involuntary muscle dysfunction is also a treatment taught to relieve the pain associated with fibromyalgia. (S. K. Yue, Method of treating myofascial pain syndrome with relaxin, U.S. Pat. No. 5,863,552). However, there has been no known cause of FM to which diagnosis and/or treatment could be directed.
Chronic fatigue syndrome (CFS) affects more than a half million Americans. (P. H. Levine, What we know about chronic fatigue syndrome and its relevance to the practicing physician, Am. J. Med. 105(3A):100S–03S [1998]). Chronic fatigue syndrome is characterized by a sudden onset of persistent, debilitating fatigue and energy loss that lasts at least six months and cannot be attributed to other medical or psychiatric conditions; symptoms include headache, cognitive and behavioral impairment, sore throat, pain in lymph nodes and joints, and low grade fever. (M. Terman et al., Chronic Fatigue Syndrome and Seasonal; Affective Disorder: Comorbidity, Diagnostic Overlap, and Implications for Treatment, Am. J. Med. 105(3A). 115S–24S [1998]). Depression and related symptoms are also common, including sleep disorders, anxiety, and worsening of premenstrual symptoms or other gynecological complications. (A. L. Komaroff and D. Buchwald, Symptoms and signs of chronic fatigue syndrome, Rev. Infect. Dis. 13:S8–S11 [1991]; B. L. Harlow et al., Reproductive correlates of chronic fatigue syndrome, Am. J. Med. 105(3A):94S–99S [1998]). Other physiologic abnormalities are also associated with CFS in many patients, including neurally-mediated hypotension, hypocortisolism, and immunologic dysregulation. (P. H. Levine [1998]). A subgroup of CFS patients complain of exacerbated mood state, diminished ability to work and difficulty awakening during winter months, reminiscent of seasonal affective disorder. (M. Terman et al. [1998]).
The etiology of CFS has been unknown, and the heterogeneity of CFS symptoms has precluded the use of any particular diagnostic laboratory test. (P. H. Levine [1998]). Symptomatic parallels have been suggested between CFS and a number of other disease conditions, resulting from viral infection, toxic exposure, orthostatic hypotension, and stress, but none of these has been shown to have a causal role in CFS. (E.g., I. R. Bell et al., Illness from low levels of environmental chemicals: relevance to chronic fatigue syndrome and fibromyalgia, Am. J. Med. 105(3A):74S–82S [1998]; R. L. Bruno et al., Parallels between post-polio fatigue and chronic fatigue syndrome: a common pathophysiology?, Am. J. Med. 105(3A):66S–73S [1998]; R. Glaser and J. K. Kiecolt-Glaser, Stress-associated immune modulation: relevance to viral infections and chronic fatigue syndrome, Am. J. Med. 105(3A):35S–42S [1998]; P. C. Rowe and H. Calkins, Neurally mediated hypotension and chronic fatigue syndrome, Am. J. Med. 105(3A):15S–21S [1998], L. A. Jason et al., Estimating the prevalence of chronic fatigue syndrome among nurses, Am. J. Med. 105(3A):91S–93S [1998]). One study reported that there was no support for an etiological role in CFS of Yersinia enterocolitica infection. (C. M. Swanink et al., Yersinia entercolitica and the chronic fatigue syndrome, J. Infect. 36(3):269–72 [1998]). Accordingly, there has been no known cause to which diagnosis and/or treatment of CSF could be directed.
Consequently, the diagnosis and treatment of CFS have continued to be directed to symptoms, rather than to an underlying treatable cause. For example, the use of relaxin has been described for relaxing the involuntary muscles and thus relieve pain associated with CFS. (S. K. Yue, Method of treating myofascial pain syndrome with relaxin, U.S. Pat. No. 5,863,552).
Attention deficit/hyperactivity disorder (ADHD) is a heterogeneous behaviorial disorder of unknown etiology that always appears first in childhood, affecting 3–20% of elementary school-age children, and continues to affect up to 3% of adults. (Reviewed in L. L. Greenhill, Diagnosing attention deficit/hyperactivity disorder in children, J. Clin. Psychiatry 59 Suppl 7:31–41 [1998]). Those affected with ADHD symptoms typically exhibit inattentiveness and distractability (AD type), hyperactive and impulsive behavior (HI type), or a combination of these, to a degree that impairs normal functioning and is often socially disruptive. (M. L. Wolraich et al., Examination of DSM-IV criteria for attention deficit/hyperactivity disorder in a county-wide sample, J. Dev. Behav. Pediatr. 19(3):162–68 [1998]; J. J. Hudziak et al., Latent class and factor analysis of DSM-IV ADHD: a twin study of female adolescents, J. Am. Acad. Child Adolesc. Psychiatry 37(8):848–57 [1998]). Often prescribed are central nervous system stimulants, tricyclic antidepressants, antihypertensives, analgesics, or antimanic drugs, but there has been no known cause of ADHD to which diagnosis and/or treatment could be directed. (S. C. Schneider and G. Tan, Attention deficit/hyperactivity disorder. In pursuit of diagnostic accuracy, Postgrad. Med. 101(4):231–2, 235–40 [1997]; W. J. Barbaresi, Primary-care approach to the diagnosis and management of attention deficit/hyperactivity disorder, Mayo Clin. Proc. 71(5):463–71 [1996]).
There has also been no known cause for autoimmune diseases, including multiple sclerosis and systemic lupus erythematosus. Multiple sclerosis (MS) is a neurologic disease that primarily strikes teens and young adults under 35 years. Affecting 350,000 Americans, MS is the most frequent cause of neurologic disability except for traumatic injuries; MS affects twice as many females compared to males. (S. L. Hauser, Multiple Sclerosis and other demyelinating diseases In: Harrison's Principles of Internal Medicine, 13th ed., K. J. Isselbacher et al. (eds.), McGraw-Hill, pp.2287–95 [1994]). The disease is characterized by chronic inflammation, scarring, and selective destruction of the myelin sheath around neural axons of the central nervous system, and is thought to be caused by autoimmune responses. A treatment for MS taught by Weiner et al. is related to oral administration of autoantigens to the patient to suppress the autoimmune response by eliciting suppressor T-cells specific for myelin basic protein (MBP). There are no specific diagnostic tests for MS; diagnosis is based on clinical recognition of destructive patterns of central nervous system injury that are produced by the disease. (S. L. Hauser [1994]) Nerve damage may be mediated by cytokines, especially TNF-α, which has been found to be selectively toxic to myelin and to oligodendrocytes in vitro. Elevated levels of TNF-α and IL-2 were measured in MS patients. (J. L. Trotter et al., Serum cytokine levels in chronic progressive multiple sclerosis: interleukin-2 levels parallel tumor necrosis factor-alpha levels, J. Neuroimmunol. 33(1):29–36 [1991]; H. L. Weiner et al., Treatment of multiple sclerosis by oral administration of autoantigens, U.S. Pat. No. 5,869,054). Another treatment for MS involves the administration of a vitamin D compound. (H. F. DeLuca et al., Multiple sclerosis treatment, U.S. Pat. No. 5,716,946). However, there has been no known cause of MS to which diagnosis and/or treatment could be directed.
Systemic lupus erythematosus (SLE) is an autoimmune rheumatic disease characterized by deposition in tissues of autoantibodies and immune complexes leading to tissue injury (B. L. Kotzin, Systemic lupus erythematosus, Cell 85:303–06 [1996]). In contrast to autoimmune diseases such as MS and type 1 diabetes mellitus, SLE potentially involves multiple organ systems directly, and its clinical manifestations are diverse and variable. (Reviewed by B. L. Kotzin and J. R. O'Dell, Systemic lupus erythematosus, In: Samler's Immunologic Diseases, 5th ed., M. M. Frank et al., eds., Little Brown & Co., Boston, pp. 667–97 [1995]). For example, some patients may demonstrate primarily skin rash and joint pain, show spontaneous remissions, and require little medication. At the other end of the spectrum are patients who demonstrate severe and progressive kidney involvement that requires therapy with high doses of steroids and cytotoxic drugs such as cyclophosphamide. (B. L. Kotzin [1996]).
The serological hallmark of SLE, and the primary diagnostic test available, is elevated serum levels of IgG antibodies to constituents of the cell nucleus, such as double-stranded DNA (dsDNA), single-stranded DNA (ss-DNA), and chromatin. Among these autoantibodies, IgG anti-dsDNA antibodies play a major role in the development of lupus glomerulonephritis (GN). (B. H. Hahn and B. Tsao, Antibodies to DNA, In: Dubois' Lupus Erythematosus, 4th ed., D. J. Wallace and B. Hahn, eds., Lea and Febiger, Philadelphia, pp. 195–201 [1993]; Ohnishi et al., Comparison of pathogenic and nonpathogenic murine antibodies to DNA: Antigen binding and structural characteristics, Int. Immunol. 6:817–30 [1994]). Glomerulonephritis is a serious condition in which the capillary walls of the kidney's blood purifying glomeruli become thickened by accretions on the epithelial side of glomerular basement membranes. The disease is often chronic and progressive and may lead to eventual renal failure.
The mechanisms by which autoantibodies are induced in these autoimmune diseases remains unclear. As there has been no known cause of SLE, to which diagnosis and/or treatment could be directed, treatment has been directed to suppressing immune responses, for example with macrolide antibiotics, rather than to an underlying cause. (E.g., Hitoshi et al., Immunosuppressive agent, U.S. Pat. No. 4,843,092).
Another disorder for which immunosuppression has been tried is Crohn's disease. Crohn's disease symptoms include intestinal inflammation and the development of intestinal stenosis and fistulas; neuropathy often accompanies these symptoms. Anti-inflammatory drugs, such as 5-aminosalicylates (e.g., mesalamine) or corticosteroids, are typically prescribed, but are not always effective. (Reviewed in V. A. Botoman et al., Management of Inflammatory Bowel Disease, Am. Fam. Physician 57(1):57–68 [1998]). Immunosuppression with cyclosporine is sometimes beneficial for patients resistant to or intolerant of corticosteroids. (J. Brynskov et al., A placebo-controlled, double-blind, randomized trial of cyclosprorine therapy in active chronic Crohn's disease, N. Engl. J. Med. 321(13):845–50 [1989]).
Nevertheless, surgical correction is eventually required in 90% of patients; 50% undergo colonic resection. (K. Leiper et al., Adjuvant post-operative therapy, Baillieres Clin. Gastroenterol. 12(1): 179–99 [1998]; F. Makowiec et al., Long-term follow-up after resectional surgery in patients with Crohn's disease involving the colon, Z. Gastroenterol. 36(8):619–24 [1998]). The recurrence rate after surgery is high, with 50% requiring further surgery within 5 years. (K. Leiper et al. [1998]; M. Besnard et al., Postoperative outcome of Crohn's disease in 30 children, Gut 43(5):634–38 [1998]).
One hypothesis for the etiology of Crohn's disease is that a failure of the intestinal mucosal barrier, possibly resulting from genetic susceptibilities and environmental factors (e.g., smoking), exposes the immune system to antigens from the intestinal lumen including bacterial and food antigens (e.g., Söderholm et al., Epithelial permeability to proteins in the non-inflamed ileum of Crohn's disease?, Gastroenterol. 117:65–72 [1999]; D. Hollander et al., Increased intestinal permeability in patients with Crohn's disease and their relatives. A possible etiologic factor, Ann. Intern. Med. 105:883–85 [1986]; D. Hollander, The intestinal permeability barrier. A hypothesis to its involvement in Crohn's disease, Scand. J. Gastroenterol. 27:721–26 [1992]). Another hypothesis is that persistent intestinal infection by pathogens such as Mycobacterium paratuberculosis, Listeria monocytogenes, abnormal Escherichia coli, or paramyxovirus, stimulates the immune response; or alternatively, symptoms result from a dysregulated immune response to ubiquitous antigens, such as normal intestinal microflora and the metabolites and toxins they produce. (R. B. Sartor, Pathogenesis and Immune Mechanisms of Chronic Inflammatory Bowel Diseases, Am. J. Gastroenterol. 92(12):5S–11 S [1997]). The presence of IgA and IgG anti-Sacccharomyces cerevisiae antibodies (ASCA) in the serum was found to be highly diagnostic of pediatric Crohn's disease. (F. M. Ruemmele et al., Diagnostic accuracy of serological assays in pediatric inflammatory bowel disease, Gastroenterol. 115(4):822–29 [1998]; E. J. Hoffenberg et al., Serologic testing for inflammatory bowel disease, J. Pediatr. 134(4):447–52 [1999]).
In Crohn's disease, a dysregulated immune response is skewed toward cell-mediated immunopathology. (S. I. Murch, Local and systemic effects of macrophage cytokines in intestinal inflammation, Nutrition 14:780–83 [1998]). But immunosuppressive drugs, such as cyclosporine, tacrolimus, and mesalamine have been used to treat corticosteroid-resistant cases of Crohn's disease with mixed success. (J. Brynskov et al. [1989]; K. Fellerman et al., Steroid-unresponsive acute attacks of inflammatory bowel disease: immunomodulation by tacrolimus [FK506], Am. J. Gastroenterol. 93(10):1860–66 [1998]). An abnormal increase in colonic permeability is also seen in patients with Crohn's disease. (Vermeire S. et al, Anti-Saccharomyces cerevisiae antibodies (ASCA), phenotypes of IBD, and intestinal permeability: a study in IBD families, Inflamm Bowel Dis. 7(1):8–15 [2001]).
Recent efforts to develop diagnostic and treatment tools against Crohn's disease have focused on the central role of cytokines. (S. Schreiber, Experimental immunomodulatory therapy of inflammatory bowel disease, Neth. J. Med. 53(6):S24–31 [1998]; R. A. van Hogezand and H. W. Verspaget, The future role of anti-tumour necrosis factor-alpha products in the treatment of Crohn's disease, Drugs 56(3):299–305 [1998]). Cytokines are small secreted proteins or factors (5 to 20 kD) that have specific effects on cell-to-cell interactions, intercellular communication, or the behavior of other cells. Cytokines are produced by lymphocytes, especially TH1 and TH2 lymphocytes, monocytes, intestinal macrophages, granulocytes, epithelial cells, and fibroblasts. (Reviewed in G. Rogler and T. Andus, Cytokines in inflammatory bowel disease, World J. Surg. 22(4):382–89 [1998]; H. F. Galley and N. R. Webster, The immuno-inflammatory cascade, Br. J. Anaesth. 77:11–16 [1996]). Some cytokines are pro-inflammatory (e.g., tumor necrosis factor [TNF]-α, interleukin [IL]-1 (α and β), IL-6, IL-8, IL-12, or leukemia inhibitory factor [LIF]); others are anti-inflammatory (e.g., IL-1 receptor antagonist [IL-1ra], IL-4, IL-10, IL-11, and transforming growth factor [TGF]-β). However, there may be overlap and functional redundancy in their effects under certain inflammatory conditions.
In active cases of Crohn's disease, elevated concentrations of TNF-α and IL-6 are secreted into the blood circulation, and TNF-α, IL-1, IL-6, and IL-8 are produced in excess locally by mucosal cells. (Id.; K. Funakoshi et al., Spectrum of cytokine gene expression in intestinal mucosal lesions of Crohn's disease and ulcerative colitis, Digestion 59(1):73–78 [1998]). These cytokines can have far-ranging effects on physiological systems including bone development, hematopoiesis, and liver, thyroid, and neuropsychiatric function. Also, an imbalance of the IL-1β/IL-1ra ratio, in favor of pro-inflammatory IL-1β, has been observed in patients with Crohn's disease. (G. Rogler and T. Andus [1998]; T. Saiki et al., Detection of pro- and anti-inflammatory cytokines in stools of patients with inflammatory bowel disease, Scand. J. Gastroenterol. 33(6):616–22 [1998]; S. Dionne et al., Colonic explant production of IL-1 and its receptor antagonist is imbalanced in inflammatory bowel disease (IBD), Clin. Exp. Imunol. 112(3):435–42 [1998]; But see S. Kuboyama, Increased circulating levels of interleukin-1 receptor antagonist in patients with inflammatory bowel disease, Kurume Med. J. 45(1):33–37 [1998]). One study suggested that cytokine profiles in stool samples could be a useful diagnostic tool for Crohn's disease. (T. Saiki et al. [1998]).
Treatments that have been proposed for Crohn's disease include the use of various cytokine antagonists (e.g., IL-1ra), inhibitors (e.g., of IL-1β converting enzyme and antioxidants) and anti-cytokine antibodies. (G. Rogler and T. Andus [1998]; R. A. van Hogezand and H. W. Verspaget [1998]; J. M. Reimund et al., Antioxidants inhibit the in vitro production of inflammatory cytokines in Crohn's disease and ulcerative colitis, Eur. J. Clin. Invest. 28(2):145–50 [1998]; N. Lugering et al., Current concept of the role of monocytes/macrophages in inflammatory bowel disease-balance of pro-inflammatory and immunosuppressive mediators, Ital. J. Gastroenterol. Hepatol. 30(3):338–44 [1998]; M. E. McAlindon et al., Expression of interleukin 1 beta and interleukin 1 beta converting enzyme by intestinal macrophages in health and inflammatory bowel disease, Gut 42(2):214–19 [1998]). In particular, monoclonal antibodies against TNF-α have been tried with some success in the treatment of Crohn's disease. (S. R. Targan et al., A short-term study of chimeric monoclonal antibody cA2 to tumor necrosis factor alpha for Crohn's disease. Crohn's Disease cA2 Study Group, N. Engl. J. Med. 337(15):1029–35 [1997]; W. A. Stack et al., Randomised controlled trial of CDP571 antibody to tumour necrosis factor-alpha in Crohn's disease, Lancet 349(9051):521–24 [1997]; H. M. van Dullemen et al., Treatment of Crohn's disease with anti-tumor necrosis factor chimeric monoclonal antibody (cA2), Gastroenterol. 109(1):129–35 [1995]).
Another approach to the treatment of Crohn's disease has focused on at least partially eradicating the bacterial community that may be triggering the inflammatory response and replacing it with a non-pathogenic community. For example, McCann et al. (McCann et al., Method for treatment of idiopathic inflammatory bowel disease, U.S. Pat. No. 5,599,795) disclosed a method for the prevention and treatment of Crohn's disease in human patients. Their method was directed to sterilizing the intestinal tract with at least one antibiotic and at least one anti-fungal agent to kill off the existing flora and replacing them with different, select, well-characterized bacteria taken from normal humans. Borody taught a method of treating Crohn's disease by at least partial removal of the existing intestinal microflora by lavage and replacement with a new bacterial community introduced by fecal inoculum from a disease-screened human donor or by a composition comprising Bacteroides and Escherichia coli species. (T. J. Barody, Treatment of gastro-intestinal disorders with a fecal composition or a composition of bacteroides and E. coli, U.S. Pat. No. 5,443,826). However, there has been no known cause of Crohn's disease to which diagnosis and/or treatment could be directed.
Pain is a common symptom associated with irritable bowel syndrome, fibromyalgia, chronic fatigue syndrome, chronic pelvic pain syndrome, depression, ADHD, autoimmune diseases, and Crohn's disease. While the experience of pain is intertwined with a person's emotions, memory, culture, and psychosocial situation (D. A. Drossman and W. G. Thompson, Irritable bowel syndrome: a graduated, multicomponent treatment approach, Ann. Intern. Med. 116:1009–16 [1992]), evidence shows that certain cytokine mediated-immune responses can influence the perception of pain. Cytokines can be released in response to a variety of irritants and can modulate the perception of pain. For example, exposure of human bronchial epithelial cells to irritants, including acidic pH, results in a receptor-mediated release of inflammatory cytokines IL-6, IL-8, and TNF-β. (B. Veronesi et al., Particulate Matter initiates inflammatory cytokine release by activation of capsaicin and acid receptors in a human bronchial epithelial cell line, Toxicol. Appl. Pharmacol. 154:106–15 [1999]). Irritant receptors on cell surfaces, e.g., receptors sensitive to noxious stimuli, such as capsaicin and pH, mediate the release of cytokines and also mediate the release of neuropeptides from sensory nerve fibers, which is known to result in a neurogenic inflammatory processes and hyperalgesia (excessive sensitivity to pain). (Id.; R. O. P. de Campos et al., Systemic treatment with Mycobacterium bovis bacillus calmett-guerin (BCG) potentiates kinin B1 receptor agonist-induced nociception and oedema formation in the formalin test in mice, Neuropeptides 32(5):393–403 [1998]).
The perception of pain, is also influenced by the mediation of kinin B1 and B2 receptors, which bind peptides called kinins, e.g., the nonapeptide bradykinin or the decapeptide kallidin (lysyl bradykinin). While the precise mechanism of action is unknown, kinins cause the release of other pro-inflammatory and hyperalgesic mediators such as neuropeptides. Cytokines IL-1(α and β), IL-2, IL-6, and TNF-α are thought to activate kinin B1 receptor, and thus can contribute to enhanced perception of pain. (R. O. P. de Campos et al. [1998]. The endotoxin of Escherichia coli significantly activated kinin B1 receptor-mediated neurogenic and inflammatory pain responses in animals. (M. M. Campos et al., Expression of B1 kinin receptors mediating paw oedema formalin-induced nociception. Modulation by glucocorticoids, Can. J. Physiol. Pharmacol. 73:812–19 [1995]).
It has also been shown that IL-1β, IL-6, and TNF-α, administered to the mammalian brain, can modulate pain perception via prostaglandin-dependent processes. (T. Hori et al., Pain modulatory actions of cytokines and prostaglandin E2 in the Brain, Ann. N.Y. Acad. Sci. 840:269–81 [1998]). Granulocytes, which accumulate in nearly all forms of inflammation, are non-specific amplifiers and effectors of specific immune responses, and they can also modulate the perception of pain. Neutrophils, a type of granulocyte cell, are known to accumulate in response to IL-1β, and neutrophil accumulation plays a crucial positive role in the development of nerve growth factor (NGF)-induced hyperalgesia. (G. Bennett et al., Nerve growth factor induced hyperalgesia in the rat hindpaw is dependent on circulating neutrophils, Pain 77(3):315–22 [1998]; see also E. Feher et al., Direct morphological evidence of neuroimmunomodulation in colonic mucosa of patients with Crohn's disease, Neuroimmunomodulation 4(5–6):250–57 [1997]).
Visceral hyperalgesia, or pain hypersensitivity, is a common clinical observation in small intestinal bacterial overgrowth (SIBO), Crohn's disease, chronic pelvic pain syndrome, and irritable bowel syndrome (IBS). As many as 60% of subjects with IBS have reduced sensory thresholds for rectal distension compared to normal subjects. (H. Mertz et al., Altered rectal perception is a biological marker of patients with the irritable bowel syndrome, Gastroenterol.109:40–52 [1995]). While the experience of pain is intertwined with a person's emotions, memory, culture, and psychosocial situation (D. A. Drossman and W. G. Thompson, Irritable bowel syndrome: a graduated, multicomponent treatment approach, Ann. Intern. Med. 116:1009–16 [1992]) and the etiology for this hyperalgesia has remained elusive, evidence shows that certain cytokine mediated-immune responses can influence the perception of pain. Cytokines, including IL-1(α and β), IL-2, IL-6, and TNF-α, can be released in response to a variety of irritants and can modulate the perception of pain, possibly through the mediation of kinin B1 and/or B2 receptors (see, M. M. Campos et al., Expression of B1 kinin receptors mediating paw oedema formalin-induced nociception. Modulation by glucocorticoids, Can. J. Physiol. Pharmacol. 73:812–19 [1995]; R. O. P. de Campos et al., Systemic treatment with Mycobacterium bovis bacillus calmett-guerin (BCG) potentiates kinin B1 receptor agonist-induced nociception and oedema formation in the formalin test in mice, Neuropeptides 32(5):393–403 [1998]). Cytokine and neuropeptide levels are altered in IBS. An increase in substance P (neuropeptide)-sensitive nerve endings has been observed in subjects with IBS. (X. Pang et al., Mast cell substance P-positive nerve involvement in a patient with both irritable bowel syndrome and interstitial cystitis, Urology 47:436–38 [1996]). It has also been hypothesized that there is a sensitization of afferent pathways in IBS. (E. A. Mayer et al., Basic and clinical aspects of visceral hyperalgesia, Gastroenterol 1994;107:271–93 [1994]; L. Bueno et al., Mediators and pharmacology of visceral sensitivity: from basic to clinical investigations, Gastroenterol. 112:1714–43 [1997]).
Fibromyalgia, typically involving global musculoskeletal and/or cutaneous pain, is, by definition; a hyperalgesic state since the American College of Rheumatology defines fibromyalgia as a history of global pain in the setting of 11 out of 18 predefined tender points. (F. Wolfe et al., The American College of Rheumatology 1990 criteria for the classification of fibromyalgia, Arthritis Rheum. 33:160–72 [1990]). Evidence implies that the hyperalgesia of fibromyalgia is not simply trigger point-related but rather a global hyperalgesia. (L. Vecchiet et al., Comparative sensory evaluation of parietal tissues in painful and nonpainful areas in fibromyalgia and myofascial pain syndrome, In: Gebhart G F, Hammond D L, Jensen T S, editors, Progress in Pain Research and Management, Vol. 2, Seattle: IASP Press, pp. 177–85 [1994]; J. Sorensen et al., Hyperexcitability in fibromyalgia, J. Rheumatol. 25:152–55 [1998]).
Cytokine and neuropeptide levels are altered in IBS, fibromyalgia, and Crohn's disease. It has been shown that levels of substance P, a neuropeptide associated with nociception, are elevated in the cerebrospinal fluid of subjects with fibromyalgia. (H. Vaeroy et al., Elevated CSF levels of substance P and high incidence of Raynaud's phenomenon in patients with fibromyalgia: new features for diagnosis, Pain 32:21–26 [1988]; I. J. Russell et al., Elevated cerebrospinal fluid levels of substance P in patients with the fibromyalgia syndrome, Arthritis Rheum. 37:1593–1601 [1994]). And an increase in substance P-sensitive nerve endings has been observed in subjects with IBS and Crohn's disease. (X. Pang et al., Mast cell substance P-positive nerve involvement in a patient with both irritable bowel syndrome and interstitial cystitis, Urology 47:436–38 [1996]; (C. R. Mantyh et al., Receptor binding sites for substance P, but not substance K or neuromedin K, are expressed in high concentrations by arterioles, venules, and lymph nodules in surgical specimens obtained from patients with ulcerative colitis and Crohn's disease, Proc. Natl. Acad. Sci. 85:3235–39 [1988]; S. Mazumdar and K. M. Das, Immunocytochemical localization of vasoactive intestinal peptide and substance P in the colon from normal subjects and patients with inflammatory bowel disease, Am. J. Gastrol. 87:176–81 [1992]; C. R. Mantyh et al., Differential expression of substance P receptors in patients with Crohn's disease and ulcerative colitis, Gastroenterol. 1995;109:850–60 [1995]).
Patients with chronic pelvic pain are usually evaluated and treated by gynecologists, gastroenterologists, urologists, and internists, but in many patients with chronic pelvic pain the examination and work-up remain unrevealing, and no specific cause of the pain, such as endometriosis, can be identified. In these cases the patient is commonly said to be suffering from a “chronic pelvic pain syndrome.” Once the diagnosis of chronic pelvic pain is made, treatment is typically directed to symptomatic pain management, rather than to an underlying cause. (Wesselmann U, Czakanski P P, Pelvic pain: a chronic visceral pain syndrome, Curr. Pain Headache Rep. 5 (1):13–9 [2001]).
Mental functioning and feelings of fatigue or depression can also be influenced by immune responses. Peripherally released pro-inflammatory cytokines, such as IL-1, IL-6 and TNF-α, act on brain cellular targets and have been shown to depress spontaneous and learned behavior in animals; the vagus nerve has been shown to mediate the transmissions of the immune message to the brain, resulting in production of pro-inflammatory cytokines centrally in the brain. (R. Dantzer et al., Cytokines and sickness behavior, Ann. N.Y. Acad. Sci. 840:586–90 [1998]). In addition, there is bidirectional interplay between neurotransmitters and the immune system; lymphocytes and macrophages bear surface receptors for the stress hormone corticotrophin releasing hormone (CRH), and they respond to CRH by enhanced lymphocyte proliferation and feedback upregulation of hypothalamic CRH production. (S. H. Murch [1998]).
Pituitary production of proopiomelanocortins, such as endorphins and enkephalins, is upregulated by IL-1 and IL-2, possibly mediated by CRH, and lymphocytes and macrophages recognize these endogenous opiates via surface receptors. (S. H. Murch [1998]). Lymphocytes (TH2) and macrophages also produce and process enkephalin to an active form. Macrophage-derived cytokines, such as TNF-α, IL-1, and IL-6, are known to modulate neurotransmitter release and to affect overall neural activity; cytokines can induce classic illness behavior such as somnolence, apathy, depression, irritability, confusion, poor memory, impaired mental concentration, fever and anorexia.
While immunological responses of various severities can lead to symptoms characteristic of irritable bowel syndrome, fibromyalgia, chronic pevic pain syndrome, chronic fatigue syndrome, impaired mentation and/or memory, depression, autism, ADHD, autoimmune diseases, and Crohn's disease, there has been a definite need to determine a causal factor, for each of these diagnostic categories, to which diagnostic testing and treatment can be directed effectively.
SIBO has, until recently, mostly been suspected in subjects with significant malabsorptive sequelae. Most of the described cases of SIBO involve anatomic alterations such as physical obstruction (E. A. Deitch et al., Obstructed intestine as a reservoir for systemic infection, Am. J. Surg. 159:394 [1990]), surgical changes (e.g., L. K. Enander et al., The aerobic and anaerobic microflora of the gastric remnant more than 15 years after Billroth II resection, Scand. J. Gastroenterol. 17:715–20 [1982]), direct communication of the small intestine with colonic contents such as fistulae (O. Bergesen et al., Is vitamin B12 malabsorption in bile fistula rats due to bacterial overgrowth? A study of bacterial metabolic activity in the small bowel, Scand. J. Gastroenterol. 23:471–6 [1988]) and ileocecal valve dysfunction (surgical or otherwise) (W. O. Griffin, Jr, et al., Prevention of small bowel contamination by ileocecal valve, S. Med. J.64: 1056–8 [1971]; P. Rutgeerts et al., Ileal dysfunction and bacterial overgrowth in patients with Crohn's disease, Eur. J. Clin. Invest. 11:199–206 [1981]). Less commonly, SIBO has been associated with chronic pancreatitis (E. Trespi and A. Ferrieri, Intestinal bacterial overgrowth during chronic pancreatitis, Curr. Med. Res. Opin. 15:47–52 [1999]), hypochlorhydria (e.g., S. P. Pereira et al., Drug-induced hypochlorhydria causes high duodenal bacterial counts in the elderly, Aliment. Pharmacol. Ther. 12:99–104 [1998]), and immunodeficiency (C. Pignata et al., Jejunal bacterial overgrowth and intestinal permeability in children with immunodeficiency syndromes, Gut 31:879–82 [1990]; G. M. Smith et al., Small intestinal bacterial overgrowth in patients with chronic lymphocytic leukemia, J. Clin. Pathol. 43:57–9 [1990]).
SIBO has been associated with infections of the abdominal cavity in cases of alcoholic cirrhosis. (F. Casafont Morencos et al., Small bowel bacterial overgrowth in patients with alcoholic cirrhosis, Dig. Dis. Sci. 40(6):1252–1256 [1995]; J. Chesta et al., Abnormalities in proximal small bowel motility in patients with cirrhosis, Hepatology 17(5): 828–32 [1993]; C. S. Chang et al., Small intestine dysmotility and bacterial overgrowth in cirrhotic patients with spontaneous bacterial peritonitis, Hepatology 28(5)1187–90 [1998]). SIBO has also been associated with symptoms of chronic diarrhea, anorexia or nausea in elderly patients, and the prevalence of overgrowth in subjects over 75 years old is reported to be as high as 79% even in the absence of clinically evident clues of overgrowth or achlorhydria. (S. M. Riordan et al., Small intestinal bacterial overgrowth in the symptomatic elderly, Am. J. Gastroenterol. 92(1):47–51 [1997]). SIBO is also associated with chronic digestive symptoms in children, especially infants under two years of age (D. De Boissieu et al., Small-bowel bacterial overgrowth in children with chronic digestive diarrhea, abdominal pain, or both, J. Pediatr. 128(2):203–07 [1996]), and with chronic diarrhea after liver transplantation in children. (D. R. Mack et al., Small bowel bacterial overgrowth as a cause of chronic diarrhea after liver transplantation in children, Liver Transpl. Surg. 4(2): 166–69 [1998]).
Although diabetic enteropathy (F. Goldstein et al., Diabetic diarrhea and steatorrhea. Microbiologic and clinical observations, Ann. Intern. Med. 1970;72:215–8 [1970]), idiopathic intestinal pseudo-obstruction (A. J. Pearson et al., Intestinal pseudo-obstruction with bacterial overgrowth in the small intestine, Am. J. Dig. Dis. 14:200–05 [1969]) and scleroderma (I. J. Kahn et al., Malabsorption in intestinal scleroderma; Correction with antibiotics, N. Engl. J. Med. 274: 1339–44 [1966]) are all known to produce motility disturbances leading to SIBO. Two previous reports have examined small bowel motility among anatomically and medically naive SIBO subjects. (G. Vantrappen et al., The interdigestive motor complex of normal subjects and patients with bacterial overgrowth of the small intestine, J. Clin. Invest. 59: 1158–66 [1977]; P. O. Stotzer et al., Interdigestive and postprandial motility in small-intestinal bacterial overgrowth, Scand. J. Gastroenterol. 31:875–80 [1996]). These authors suggest that the majority of subjects with SIBO in the absence of other predisposing conditions, lack the phase III of interdigestive motility during short term recordings.
Phase III of interdigestive motility is a period of phasic contractions propagating through the length of the small intestine, approximately once every 87.2±5.4 minutes in the fasting state. (E. E. Soffer et al., Prolonged ambulatory duodeno-jejunal manometry in humans: Normal values and gender effect, Am. J. Gastrol. 93: 1318–23 [1998]). This fasting event is responsible for sweeping residue including small bowel contaminants, such as accumulated bacteria, into the colon in preparation for the next meal. (V. B. Nieuwenhujuijs et al., The role of interdigestive small bowel motility in the regulation of gut microflora, bacterial overgrowth, and bacterial translocation in rats, Ann. Surg. 228: 188–93 [1998]; E. Husebye, Gastrointestinal motility disorders and bacterial overgrowth, J Intem. Med. 237:419–27 [1995]). The endogenous peptide, motilin, is involved in the mediation of this event. (G. Vantrappen et al., Motilin and the interdigestive migrating motor complex in man, Dig. Dis. Sci. 24:497–500 [1979]). Other prokinetic agents, such as erythromycin, are believed to act on the motilin receptor and have been shown to rapidly induce an interdigestive motility event in dogs and humans. (M. F. Otterson and S. K. Sarna, Gastrointestinal motor effect of erythromycin, Am. J. Physiol. 259:G355–63; T. Tomomasa et al., Erythromycin induces migrating motor complex in human gastrointestinal tract, Dig. Dis. Sci. 31:157–61 [1986]).
In general, the speed of transit through the small intestine is normally regulated by inhibitory mechanisms located in the proximal and distal small intestine known as the jejunal brake and the ileal brake. Inhibitory feedback is activated to slow transit when end products of digestion make contact with nutrient sensors of the small intestine. (E.g., Lin, H. C., U.S. Pat. No. 5,977,175; Dobson, C. L. et al., The effect of oleic acid on the human ileal brake and its implications for small intestinal transit of tablet formulations, Pharm. Res. 16(1):92–96 [1999]; Lin, H. C. et al., Intestinal transit is more potently inhibited by fat in the distal (Ileal brake) than in the proximal (jejunal brake) gut, Dig. Dis. Sci. 42(1): 19–25[1997]; Lin, H. C. et al., Jejunal brake: inhibition of intestinal transit by fat in the proximal small intestine, Dig. Dis. Sci., 41(2):326–29 [1996a]).
Specifically, jejunal and ileal brakes slow transit by the release of gut peptides such as peptide YY and by the activation of neural pathways such as those involving endogenous opioids. (Lin, H. C. et al., Fat-induced ileal brake in the dog depends on peptide YY, Gastroenterol. 110(5):1491–95 [1996b]). Transit is then slowed by the stimulation of nonpropagative intestinal contractions which inhibit movement of the lumenal content. The removal or impairment of these inhibitory mechanisms can lead to abnormally rapid transit. For example, in patients with a history of resection of the terminal ileum, intestinal transit can become uncontrolled and abnormally accelerated when the ileal brake is no longer intact. Time for processing of food can then be so reduced that few end products of digestion are available to trigger the jejunal brake as the remaining inhibitory mechanism.
Peptide YY and its analogs or agonists have been used to manipulate endocrine regulation of cell proliferation, nutrient transport, and intestinal water and electrolyte secretion. (E.g., Balasubramaniam, Analogs of peptide yy and uses thereof, U.S. Pat. No. 5,604,203; WO9820885A1; EP692971A1; Croom et al., Method of enhancing nutrient uptake, U.S. Pat. No. 5,912,227; Litvak, D. A. et al., Characterization of two novel proabsorptive peptide YY analogs, BIM-43073D and BIM-43004C, Dig. Dis. Sci. 44(3):643–48 [1999]). A role for peptide YY in the regulation of intestinal motility, secretion, and blood flow has also been suggested, as well as its use in a treatment of malabsorptive disorders (Liu, C. D. et al., Peptide YY: a potential proabsorbtive hormone for the treatment of malabsorptive disorders, Am. Surg. 62(3):232–36 [1996]; Liu, C. D. et al., Intralumenal peptide YY induces colonic absorption in vivo, Dis. Colon Rectum 40(4):478–82 [1997]; Bilchik, A. J. et al., Peptide YY augments postprandial small intestinal absorption in the conscious dog, Am. J. Surg. 167(6):570–74 [1994]).
Lin et al. immuno-neutralized peptide YY in vivo to block the ileal brake response and, thus, showed that it is mediated by peptide YY. (Lin, H. C. et al., Fat-induced ideal brake in the dog depends on peptide YY, Gastroenterology, 110(5):1491–95 [1996b]). Serum levels of peptide YY increase during the ileal brake response to nutrient infusion into the distal ileum. (Spiller, R. C. et al., Further characterisation of the ‘ileal brake’ reflex in man—effect of ileal infusion of partial digests of fat, protein, and starch on jejunal motility and release of neurotensin, enteroglucagon, and peptide YY, Gut, 29(8):1042–51 [1988]; Pironi, L. et al., Fat-induced ileal brake in humans: a dose-dependent phenomenon correlated to the plasma levels of peptide YY., Gastroenterology, 105(3):733–9 [1993]; Dreznik, Z. et al, Effect of ileal oleate on interdigestive intestinal motility of the dog, Dig. Dis. Sci., 39(7):1511–8 [1994]; Lin, C. D. et al., Interlumenal peptide YY induces colonic absorption in vivo, Dis. Colon Rectum, 40(4):478–82 [April 1997]). In contrast, in vitro studies have shown peptide YY infused into isolated canine ileum dose-dependently increased phasic circular muscle activity. (Fox-Threlkeld, J. A. et al., Peptide YY stimulates circular muscle contractions of the isolated perfused canine ileum by inhibiting nitric oxide release and enchancing acetylcholine release, Peptides, 14(6):1171–78 [1993]).
Kreutter et al. taught the use of β3-adrenoceptor agonists and antagonists for the treatment of intestinal motility disorders, as well as depression, prostate disease and dyslipidemia (U.S. Pat. No. 5,627,200).
Bagnol et al. reported the comparative immunovisualization of mu and kappa opioid receptors in the various cell layers of the rat gastrointestinal tract, including a comparatively large number of kappa opioid receptors in the myenteric plexus. (Bagnol, D. et al, Cellular localization and distribution of the cloned mu and kappa opioid receptors in rat gastrointestinal tract, Neuroscience, 81(2):579–91 [1997]). They suggested that opioid receptors can directly influence neuronal activity in the gastrointestinal tract.
Kreek et al taught the use of opioid receptor antagonists, such as naloxone, naltrexone, and nalmefene, for the relief of gastrointestinal dysmotility. (Kreek et al., Method for controlling gastrointestinal dysmotility, U.S. Pat. No. 4,987,136). Riviere et al. taught the use of the opioid receptor antagonist fedotozine in the treatment of intestinal obstructions (Riviere, P. J. M. et al., U.S. Pat. No. 5,362,756). Opioid-related constipation, the most common chronic adverse effect of opioid pain medications in patients who require long-term opioid administration, such as patients with advanced cancer or participants in methadone maintenance, has been treated with orally administered methylnaltrexone and naloxone. (Yuan, C. S. et al., Methylnaltrexone for reversal of constipation due to chronic methadone use: a randomized controlled trial, JAMA 283(3):367–72 [2000]; Meissner, W. et al., Oral naloxone reverses opioid-associated constipation, Pain 84(1):105–9 [2000]; Culpepper-Morgan, J. A., et al., Treatment of opioid-induced constipation with oral naloxone: a pilot study, Clin. Pharmacol. Ther. 52(1):90–95 [1992]; Yuan, C. S. et al., The safety and efficacy of oral methylnaltrexone in preventing morphine-induced delay in oral-cecal transit time, Clin. Pharmacol. Ther. 61(4):467–75 [1997]; Santos, F. A. et al., Quinine-induced inhibition of gastrointestinal transit in mice: possible involvement of endogenous opioids, Eur. J. Pharmacol., 364(2–3):193–97 [1999]. Naloxone was also reported to abolish the ileal brake in rats (Brown, N. J. et al., The effect of an opiate receptor antagonist on the ileal brake mechanism in the rat, Pharmacology, 47(4):230–36 [1993]).
Receptors for 5-hydroxytryptamine (5-HT) have been localized on various cells of the gastrointestinal tract. (Gershon, M. D., Review article: roles played by 5-hydroxytryptamine in the physiology of the bowel, Aliment. Pharmacol. Ther., 13 Suppl 2:15–30 [1999]; Kirchgessner, A. L. et al., Identification of cells that express 5-hydroxytryptamine1A receptors in the nervous systems of the bowel and pancreas, J. Comp. Neurol., 15:364(3):439–455 [1996]). Brown et al. reported that subcutaneous administration of 5-HT3 receptor antagonists, granisetron and ondansetron, in rats delayed intestinal transit of a baked bean meal but abolished the ileal brake induced by ileal infusion of lipid. They postulated the presence of 5-HT3 receptors on afferent nerves that initiate reflexes that both accelerate and delay intestinal transit. (Brown, N. J. et al., Granisetron and ondansetron: effects on the ileal brake mechanism in the rat, J. Pharm. Pharmacol. 45(6):521–24 [1993]). Kuemmerle et al, reported neuro-endocrine 5-HT-mediation of motilin-induced accelerated gastrointestinal motility. (Kuemmerle, J. F. et al., Serotonin neural receptors mediate motilin-induced motility in isolated, vascularly perfused canine jejunum, J. Surg. Res., 45(4):357–62 [1988]).
Ninety-five percent of the human body's stores of 5-hydroxyltryptamine (5-HT), also known as serotonin, are found in the gastrointestinal tract. (Gershon, M. D., The Second Brain, New York: Harper Collins [1998]). In the intestines, the vast majority of 5-HT is located in the enterochromaffin (EC) cells of the mucosa (Gershon [1998]). 5-HT is also released by myenteric 5-HT neurons in the myenteric plexus. (Gershon, M. D., The enteric nervous system, Annu Rev Neurosci 4: 227–272 [1981]; Gershon, M. D. et al., Serotonin: synthesis and release from the myenteric plexus of the mouse intestine, Science 149: 197–199 [1965]; Holzer, P., and G. Skofitsch, Release of endogenous 5-hydroxytryptamine from the myenteric plexus of the guinea-pig isolated small intestine, Br J Pharmacol 81: 381–386 [1984]; Penttila, A., Histochemical reactions of the enterochromaffin cells and the 5-hydroxytryptamine content of the mammalian duodenum, Acta Physiol Scand Suppl 281: 1–77 [1966]). These intrinsic 5-HT neurons receive input from parasympathetic and sympathetic fibers (Gershon, M. D., and D. L. Sherman, Noradrenergic innervation of serotoninergic neurons in the myenteric plexus, J Comp Neurol 259: 193–210 [1987]) and provide input to the motor neurons in their vicinity to suggest that they are interneurons. 5-HT3 receptors are widely expressed by these myenteric 5-HT neurons as well as their neighboring neurons (Galligan, J. J., Electrophysiological studies of 5-hydroxytryptamine receptors on enteric neurons, Behav Brain Res 73: 199–201 [1996]; Zhou, X., and J. J. Galligan, Synaptic activation and properties of 5-hydroxytryptamine(3) receptors in myenteric neurons of guinea pig intestine, J Pharmacol Exp Ther 290: 803–10 [1999]). However, the physiologic function of these myenteric 5-HT neurons is not known. (E. G., Gershon, M. D. Review article: roles played by 5-hydroxytryptamine in the physiology of the bowel, Aliment Pharmacol Ther 13 Suppl 2: 15–30, 1999]; Grider, J. R. et al., 5-HT released by mucosal stimuli initiates peristalsis by activating 5-HT4/5-HT1p receptors on sensory CGRP neurons, Am J Physiol 270: G778–G782 [1996]).
Regardless of the source of 5-HT (mucosal vs. neuronal or both), the signaling role of this molecule is facilitated by the availability of a 5-HT reuptake transporter called SERT that terminates the signal with its removal. (Wade, P. R. et al, Localization and function of a 5-HT transporter in crypt epithelia of the gastrointestinal tract, J Neurosci 16: 2352–64 [1996]). Since SERT is a part of the plasma membrane of serotonergic neurons (Blakely, R. D. et al., Cloning and expression of a functional serotonin transporter from rat brain, Nature 354: 66–70 [1991]), these transporters are ideally positioned to remove neuronal 5-HT after signaling is completed. Serotonergic nerves are, however, absent from the intestinal mucosa. (Furness, J. B., and M. Costas, The enteric nervous system, New York: Churchill Livingston [1987]). Instead, mucosal 5-HT from EC cells is removed by SERT expressed by neighboring epithelial cells. (Chen, J. X. et al., Guinea pig 5-HT transporter: cloning, expression, distribution, and function in intestinal sensory reception, Am J Physiol 275: G433–G448 [1998]).
The action of SERT is blocked by drugs that inhibit the reuptake transporter. These serotonin-selective reuptake inhibitors (SSRI) are widely used as antidepressants. The most commonly prescribed example is fluoxetine (Prozac). These agents significantly alter the peristaltic response. Wade et al. reported that fluoxetine initially acclerated the passage of a pellet through an isolated segment of guinea pig colon to suggest potentiation of the peristaltic effect of 5-HT when the removal of this molecule was inhibited (Wade et al. [1996]). However, as the dose of the SSRI was increased, the transit of the pellet became slower and slower. This observation with fluoxetine suggested to Gershon that 5-HT receptors became desensitized when an excess of 5-HT stayed around for a longer period of time and traversed further away from its mucosal source (Gershon [1998]). These are then the current concepts to explain the common gastrointestinal side effects of SSRIs including nausea (excess 5-HT acting on extrinsic sensory nerves) and diarrhea (excess 5-HT acting on intrinsic primary afferent neurons to initiate peristalsis; Gershon [1998]).
The current scientific foundation for understanding the role of serotonin in normal and abnormal motility of the small intestine has been based on the role of mucosal serotonin in two enteric functions. The first is as the neurotransmitter, via the activation of intrinsic primary afferent neurons (IPAN), for the peristaltic reflex, which mediates colonic evacuation, and for the mucosal secretory reflex. (E.g., Grider, J. R. et al., 5-Hydroxytryptamine4 receptor agonists initiate the peristaltic reflex in human, rat, and guinea pig intestine, Gastroenterology, 115(2):370–80 [1998]; Jin, J. G. et al., Propulsion in guinea pig colon induced by 5-hydroxytryptamine (HT) via 5-HT4 and 5-HT3 receptors, J. Pharmacol. Exp. Ther., 288(1):93–97 [1999]; Foxx-Orenstein, A. E. et al., 5-HT4 receptor agonists and delta-opioid receptor antagonists act synergistically to stimulate colonic propulsion, Am J. Physiol., 275(5 Pt. 1):G979–83 [1998]; Foxx-Orenstein, A. E., Distinct 5-HT receptors mediate the peristaltic reflex induced by mucosal stimuli in human and guinea pig intestine, Gastroenterology 111(5):1281–90 [1996]; Wade, P. R. et al., Localization and function of a 5-HT transporter in crypt epithelia of the gastrointestinal tract, J. Neurosci., 16(7):2352–64 [1996]; Grinder, J., Gastrin-releasing peptide (GRP) neuron are excitatory neurons in the descending phase of the peristaltic reflex, Gastronenterology 116: A1000 [1999]; Cooke, H., M. Sidhu, and Y. Wang, 5-HT activates neural reflexes regulating secretion in the guinea pig colon, Neurogastroenterol Motil 9: 181–6 [1997]; Cooke, H. J., and H. V. Carey, Pharmacological analysis of 5-hydroxytryptamine actions on guinea-pig ileal mucosa, Eur J Pharmacol 111: 329–37, [1985]; Frieling, T., J. Wood, and H. Cooke, Submucosal reflexes: distension-evoked ion transport in the guinea pig distal colon, Am J Physiol 263: G91–96 [1992]; Hardcastle, J., and P. Hardcastle, Comparison of the intestinal secretory responses to 5-hydroxytryptamine in the rat jejunum and ileum in-vitro, J Pharm Pharmcacol 49: 1126–31 [1997]; Kinsman, R. I., and N. W. Read, Effect of naloxone on feedback regulation of small bowel transit by fat, Gastroenterology 87: 335–337 [1984]).
The second enteric role for 5-HT is as the signal to the brain about lumenal conditions, linking mucosal stimuli with the brain via extrinsic primary sensory neurons. (Blackshaw, L. A., and D. Grundy, Effects of 5-hydroxytryptamine on discharge of vagal mucosal afferent fibers from the upper gastrointestinal tract of the ferret, J Auton Nerv Syst 45: 41–50 [1993]). On the basis of this understanding, concepts have evolved to explain the irritable bowel syndrome as a condition of serotonin excess (leading to diarrhea from excessive peristalsis) (Gershon [1998]), even as the constipation typical of this syndrome remains puzzling. Similar explanations have also been used to explain the diarrhea reported by patients taking SSRI (e.g. Prozac).
The intestinal response to 5-HT has previously been described in terms of the peristaltic reflex in in vitro models. Bulbring and Crema first showed that lumenal 5-HT resulted in peristalsis. (Bulbring et al., J. Physiol. 140:381–407 [1959]; Bulbring et al., Brit. J. Pharm. 13:444–457 [1958]). Since the stimulation of peristalsis by 5-HT was unaffected by extrinsic denervation (Bulbring et al., QJ Exp. Physiol. 43:26–37 [1958]), the peristaltic reflex was considered to be intrinsic to the enteric nervous system. Using a modified Trendelenburg model that compartmentalized the peristaltic reflex into the sensory limb, the ascending contraction limb (orad to stimulus) and the descending relaxation limb (aborad to stimulus), Grider, et al. reported that (1) mucosal stimulation but not muscle stretch released 5-HT to activate a primary sensory neuron to release calcitonin gene-related peptide (CGRP)(Grider et al., Am. J. Physiol. 270:G778–G782 [1996]) via 5-HT4 receptors in humans and rats (also 5-HT1p in rats) and 5-HT3 receptors in guinea pigs; (2) cholinergic interneurons are then stimulated by CGRP to initiate both ascending contraction via an excitatory motor neuron that depends on substances P and K and acetylcholine (Grider et al., Am. J. Physiol. 257:G709–G714 [1989]) and descending relaxation (Grider, Am. J. Physiol. 266:G1139–G1145 [1994]; Grider et al. [1996], Jin et al., J. Pharmacol. Exp. Ther. 288:93–97 [1999]) via an inhibitory motor neuron that depends on pituitary adenylate cyclase-activating peptide (PACAP), nitric oxide and vasoactive inhibitory peptide (VIP)(Grider et al., Neuroscience 54:521–526 [1993]; Grider et al., J. Auton. Nerv. Syst. 50:151–159 [1994]); and (3) peristalsis is controlled by [a] an opioid pathway that inhibits descending relaxation by suppressing the release of VIP; [b] a somatostatin pathway that inhibits this opioid pathway (Grider, Am. J. Physiol. 275:G973–G978 [1998]); and [c] a GABA (Grider, Am. J. Physiol. 267:G696–G701 [1994]) and a gastrin releasing peptide (GRP) (Grider, Gastroenterol. 116:A1000 [1999]) pathway that stimulate VIP release. An opioid pathway that inhibits the excitatory motor neurons responsible for ascending contraction has also been described (Gintzler et al., Br. J. Pharmacol. 75:199–205 [1982]; Yau et al., Am. J. Physiol. 250:G60–G63 [1986]). These observations are consistent with neuroanatomic and electrophysiological observations.
In addition, mucosal stroking has been found to induce 5-HT release by intestinal mucosal cells, which in turn activates a 5-HT4 receptor on enteric sensory neurons, evoking a neuronal reflex that stimulates chloride secretion (Kellum, J. M. et al., Stroking human jejunal mucosa induces 5-HT release and Cl− secretion via afferent neurons and 5-HT4 receptors, Am. J. Physiol. 277(3 Pt 1):G515–20 [1999]).
Agonists of 5-HT4/5, 5-HT3 receptors, as well as opioid Δ receptor antagonists, were reported to facilitate peristaltic propulsive activity in the colon in response to mechanical stroking, which causes the endogenous release of 5-HT and calcitonin gene-related protein (CGRP) in the stroked mucosal area. (Steadman, C. J. et al., Selective 5-hydroxytrypamine type 3 receptor antagonism with ondansetron as treatment for diarrhea-predominant irritable bowel syndrome: a pilot study, Mayo Clin. Proc. 67(8):732–38 [1992]). Colonic distension also results in CGRP secretion, which is associated with triggering the peristaltic reflex. 5-HT3 receptor antagonists have been used for the treatment of autism. (E.g., Oakley et al., 5-HT3 receptor antagonists for the treatment of autism, U.S. Pat. No. 5,225,407).
Improved methods of detecting or diagnosing SIBO and SIBO-caused conditions are also a desideratum. Typically, detection of SIBO is done by detecting hydrogen and/or methane exhaled in the the breath. (E.g., P. Kerlin and L. Wong, Breath hydrogen testing in bacterial overgrowth of the small intestine, Gastroenterol. 95(4):982–88 [1988]; A. Strocchi et al., Detection of malabsorption of low doses of carbohydrate: accuracy of various breath H2 criteria, Gastroenterol 105(5):1404–1410 [1993]; D. de Boissieu et al., [1996]; P. J. Lewindon et al., Bowel dysfunction in cysticfibrosis: importance of breath testing, J. Paedatr. Child Health 34(1):79–82 [1998]). Hydrogen is a metabolic product of the fermentation of carbohydrates and amino acids by bacteria normally found in the colon. While the hydrogen that is produced in the colonic lumen may be excreted via the lungs (exhaled breath) and the anus (flatus), these routes of excretion are responsible for the elimination of only a fraction of the total amount of hydrogen (10%)that is produced in the gut (Levitt, M. D. et al., Hydrogen (H2) catabolism in the colon of the rat, J Lab clin Med 84:163–167 [1974]).
The major mechanism for the removal of hydrogen produced by bacterial fermentation is the utilization of this gas by colonic bacteria that competes to use hydrogen via one of three hydrogen disposal pathways that are mutually exclusive. These pathways depend on the metabolism of methanogenic bacteria (Levitt, M. D. et al., H2 excretion after ingestion of complex carbohydrates, Gastroenterology 92:383–389 [1987]), acetogenic bacteria (Lajoie, R. et al., Acetate production from hydrogen and [c13] carbon dioxide by the microflora of human feces, Appl Environ Microbiol 54:2723–2727 [1988]) and sufate-reducing bacteria (Gibson, G. R. et al., Occurrence of sulphate-reducing bacteria in human faeces and the relationship of dissimilatory sulphate reduction to methanogenesis in the large gut, J Appl Bactereriol 65:103–111 [1988]). Methanogenic bacteria are more efficient than the other colonic bacteria in the elimination of lumenal hydrogen. (Strocchi, A. et al., Methanogens outcompete sulphate reducing bacteria for H2 in the human colon, Gut 35:1098–1101 [1994]). Acetogenic bacteria are uncommon, being found in the intestinal populations of <5% of humans.
In the colon, sulfate-reducing bacteria reduces sulfate to hydrogen sulfide. (MacFarlane, G. T. et al., Comparison of fermentation reactions in different regions of the human colon, J Appl Bacteriol 72:57–64 [1992]). Hydrogen sulfide is more damaging to tissues than anionic sulfide or sulfydryl compounds. Intestinal bicarbonate facilitates the conversion of hydrogen sulfide produced by sulfate-reducing bacteria in the gut to anionic sulfide. (Hamilton W A: Biocorrosion: The action of sulphate-reducing bacteria, in Biochemistry of Microbial Degradation, C. Ratlidge (ed.) Dordrecht, Kluwer Academic Publishers, pages 555–570 [1994]). Since sulfate-reducing bacteria are more common in patients with the diagnosis of ulcerative colitis (Pitcher, M. C. L. et al., Incidence and activities of sulphate-reducing bacteria in gut contents of healthy subjects and patients with ulcerative colitis, FEMS Microbiol Ecol 86:103–112 [1991]), sulfate-reducing bacteria have been considered for a possible role in the pathogenesis of ulcerative colitis. (Florin, R. H. J. et al., A role for sulfate reducing bacteria in ulcerative colitis?, Gastroenterology 98:A170 [1990]). This link has been postulated to be related to the injurious effect of hydrogen sulfide in impairing the use of short chain fatty acids as fuel by colonic epithelial cells. (Roediger, W. E. W. et al., Sulphide impairment of substrate oxidation in rat colonocytes: a biochemical basis for ulcerative colitis?, Clin Sci 85:623–627 [1993]; Roediger, W. E. et al., Reducing sulfur compounds of the colon impair colonocyte nutrition: implication of ulcerative colitis, Gastroenterology 1993;104:802–809).
Currently, clinical detection of sulfur-containing gases is limited to the detection of halitosis or bad breath. (Rosenberg, M. et al., Reproducibility and sensitivity of oral malodor measurements with a protable sulphide monitor, J Dent Res. 1991 November; 70(11): 1436–40). After garlic ingestion, the presence of allyl methyl sulfide differentiates the intestine rather than the mouth as the source of the sulfur-containing volatile gas (Suarez, F. et al., Differentiation of mouth versus gut as site of origin of odoriferous breath gases after garlic ingestion, Am J Physiol 276(2 pt 1):G425–30 [1999]).
The role of sulfate-reducing bacteria in small intestinal bacterial overgrowth has not been studied, and the presence of sulfate-reducing bacteria are not detected using the standard breath testing method which typically detects only the presence of hydrogen, methane and carbon dioxide.
There remains a need for an underlying causal factor, to which diagnostic testing and treatment can be directed, for SIBO and SIBO-caused conditions, such as irritable bowel syndrome; fibromyalgia; chronic pelvic pain syndrome; chronic fatigue syndrome; autism; depression; impaired mentation and/or memory; sugar craving; ADHD; MS, SLE and other autoimmune diseases; and Crohn's disease. This and other benefits of the present invention are described herein.